With the rapid development of communication technology, the requirements people put on information transmission systems have become higher and higher. With this background, Ultra-Wideband (UWB) technology has become a research hotspot due to its advantages, such as system simplicity, low cost, low power consumption, fast data transmission, and high safety.
However, since the ultra-wideband communication consumes very high frequency bands (3.1 GHz to 10.6 GHz), within such a frequency band range, customary communications are already present, for example, the C wave band and X wave band for use in satellite communications, wireless local area networks (WLANs), and worldwide interoperability for microwave access (WiMAX). Therefore, how to address the co-channel interference is an important subject in the UWB research, and thus notch ultra-wideband filters, also known as ultra-wide band filters with trapped waves, have become the key of the design. However, the traditional design method for notched UWB filters uses cascades of multiple filters.
However, this design method increases the system volume and the design cost, meanwhile easily leads to mismatching of parts or components and lowers the efficiency of the system. In recent years, some new design concepts have emerged, for example the defected ground structure, via structure or the multi-layer low temperature co-fired ceramic (LTCC) structure. These new design methods, although achieving a specific technical progress, are still defective in terms of large-scale system integration, expansion of the notch variation range, increase of the notch width, and the like critical technologies.